An IC chip is electrically connected to a printed circuit board by a mounting method such as wire bonding, TAB or flip chip bonding.
In the wire bonding method, an IC chip is die-bonded to a printed circuit board by adhesive, the pads of the printed circuit board are connected to the pads of an IC chip by wires such as metallic wires and then a sealing resin such as a thermosetting resin or a thermoplastic resin is applied to protect the IC chip and the wires.
In the TAB method, the wires referred to as leads are connected in the block by a solder or the like and then the bumps of an IC chip and the pads of a printed circuit board are sealed by a resin.
In the flip chip bonding method, the pads of an IC chip are connected to the pads of a printed circuit board through bumps and the gaps between the pads and the bumps are filled with a resin.
In each of these mounting methods, however, the IC chip is electrically connected to the printed circuit board through connection lead members (wires, leads or bumps). The lead members tend to be cut off and eroded, thereby breaking the connection of the printed circuit board with the IC chip and causing malfunctions.
Further, in each mounting method, a thermoplastic resin such as an epoxy resin is applied to seal the IC chip so as to protect the IC chip. If bubbles are contained at the time of filling the resin, the breakage of lead members, the corrosion of the IC pads and the deterioration of reliability are derived from the bubbles. To seal members by a thermoplastic resin, it is necessary to create resin filling plungers and metallic molds in accordance with the respective members. In addition, if a thermosetting resin is employed, it is necessary to select an appropriate resin for the materials of lead members, solder resist and the like, thereby disadvantageously causing cost increase.
On the other hand, there has been conventionally proposed a technique for electrically connecting an IC chip to a printed circuit board by embedding a semiconductor device into a substrate and forming build up layers on the substrate instead of attaching the IC chip to the exterior of the printed circuit board (or package substrate) as stated above in Japanese Patent Laid-Open Nos. 9-321408 (or U.S. Pat. No. 5,875,100), 10-256429, 11-126978 and the like.
According to Japanese Patent Laid-Open No. 9-321408 (or U.S. Pat. No. 5,875,100), a semiconductor device having stud bumps formed on die pads is embedded into a printed circuit board and wirings are formed on the stud bumps to thereby electrically connect the printed circuit board to the semiconductor device. However, since the stud bumps are onion-shaped and irregular in height, smoothness is deteriorated if an interlayer insulating layer is formed and electrical connection cannot be established even if via holes are formed. Further, since the stud bumps are provided by bonding one by one, they cannot be provided collectively and productivity is thereby disadvantageously lowered.
Japanese Patent Laid-Open No. 10-256429 shows a structure in which a semiconductor device is contained in a ceramic substrate and the substrate is electrically connected to the semiconductor device by flip chip bonding. However, ceramic is inferior in outline workability and the semiconductor device cannot be appropriately contained in the ceramic substrate. Besides, the bumps are irregular in height. Due to this, the smoothness of an interlayer insulating layer is deteriorated and connection characteristic is deteriorated accordingly.
Japanese Patent Laid-Open No. 11-126978 shows a multilayer printed circuit board wherein an electrical component such as a semiconductor device is embedded into a gap or containing portion, connected to a conductor circuit and built up through via holes. However, since the containing portion is a gap, a positional error tends to occur and the substrate cannot be often connected to the pads of the semiconductor device. Besides, since die pads are directly connected to the conductor circuit, oxide coats tend to be formed on the respective die pads, thereby disadvantageously increasing insulating resistance.
The present invention has been made to improve the above-stated problems. It is an object of the present invention to provide a semiconductor device manufacturing method which allows a semiconductor device to be directly electrical connected to a printed circuit board without using lead members.
Meanwhile, if a semiconductor device is embedded into a printed circuit board made of resin, then the printed circuit board is warped by heat generated in the semiconductor device, internal wirings are cut off and reliability is thereby disadvantageously deteriorated.
The present invention has been made to improve the above-stated problem. It is, therefore, a still further object of the present invention to provide a multilayer printed circuit board into which a semiconductor device is integrated and the method of manufacturing the multilayer printed circuit board.
Furthermore, conventionally, a highly reliable printed circuit board into which a semiconductor device is integrated cannot be efficiently manufactured.
The present invention has been made to improve the above problem. It is, therefore, a still further object of the present invention to provide a manufacturing method capable of efficiently manufacturing a highly reliable multilayer printed circuit board into which a semiconductor device is integrated.
Moreover, if a multilayer printed circuit board comprising a substrate into which a semiconductor device is embedded and contained, is employed as a package substrate, a chip set or the like, the multilayer printed circuit board can fulfill its behaviors by being electrically connected to an external substrate (which is a so-called mother board or a daughter board). Due to this, it is necessary to provide BGA's and conductive connection pins (PGA's) on the multilayer printed circuit board. The BGA's and PGA's are formed by providing solder pads on a solder resist layer on the surface layer of the multilayer printed circuit board.
However, if a behavioral test or a reliability test is conducted while providing solder bumps on the surface layer of a substrate into which a semiconductor device is embedded and electrically connecting the substrate to an external substrate, it is discovered that an interlayer insulating layer, a solder resist layer, an interlayer resin insulating layer, a solder resist, solder bumps and the surroundings of the solder bumps (which means solder layers and corrosion resisting metal) are cracked and peeled, that the solder bumps are detached and that the positions of the solder bumps are slipped. Particularly, cracks occur to the pads of the semiconductor device and the cracks penetrate the interlayer insulating layer. Accordingly, it becomes clear that in the multilayer printed circuit board into which the semiconductor device is integrated, the electrical connection characteristics between solder bumps and conductor circuits is disadvantageously deteriorated and that the reliability of the multilayer printed circuit board is deteriorated accordingly.
The present invention has been made to improve the above-stated problems. It is, therefore, a still further object of the present invention to provide a multilayer printed circuit board or particularly a multilayer printed circuit board into which a semiconductor device is integrated having high electrical connection characteristics and high reliability.